Lu Hanbing, Scholl Clara A, Zuo Yantao, Stein Elliot A, Yang Yihong
Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, USA.
Magn Reson Med. 2007 Sep;58(3):616-21. doi: 10.1002/mrm.21354.
In cerebral blood volume (CBV)-weighted functional MRI (fMRI) employing superparamagnetic contrast agent, iron dose and blood oxygenation level dependent (BOLD) contamination are two important issues for experimental design and CBV quantification. Both BOLD and CBV-weighted fMRI are based upon the susceptibility effect, to which spin-echo and gradient-echo sequences have different sensitivities. In the present study, CBV-weighted fMRI was conducted using spin-echo and gradient-echo sequences at 9.4T by systematically changing the doses of contrast agent. Results suggest that BOLD contamination is a significant component in CBV-weighted fMRI at high field, particularly when relatively low dose of contrast agent is administered. A mathematical model was developed to quantify the extravascular (EV) BOLD effect. With a TE of 35 ms, the EV BOLD effect was estimated to account for 76+/-12% of the observed spin-echo fMRI signal at 9.4T. These data suggest that correcting BOLD effect may be necessary for accurately quantifying activation-induced CBV changes at high field.
在采用超顺磁性造影剂的脑血容量（CBV）加权功能磁共振成像（fMRI）中，铁剂量和血氧水平依赖（BOLD）污染是实验设计和CBV定量的两个重要问题。BOLD和CBV加权fMRI均基于磁化率效应，自旋回波和梯度回波序列对其具有不同的敏感性。在本研究中，通过系统地改变造影剂剂量，在9.4T场强下使用自旋回波和梯度回波序列进行CBV加权fMRI。结果表明，在高场强下，BOLD污染是CBV加权fMRI中的一个重要组成部分，尤其是在给予相对低剂量造影剂时。建立了一个数学模型来量化血管外（EV）BOLD效应。在TE为35 ms时，估计在9.4T场强下，EV BOLD效应占观察到的自旋回波fMRI信号的76±12%。这些数据表明，为了在高场强下准确量化激活诱导的CBV变化，校正BOLD效应可能是必要的。
